Image sensor and manufacturing method thereof

ABSTRACT

Provided are an image sensor and a method of manufacturing method of manufacturing the image sensor. The image sensor includes a substrate, photoelectric transducers and switching elements formed in layers on the substrate in this order. Each of the photoelectric transducers includes a hydrogenated amorphous silicon layer. Each of the switching elements includes an amorphous oxide semiconductor layer. The image sensor further includes a blocking layer arranged between the hydrogenated amorphous silicon layers of the photoelectric transducers and the amorphous oxide semiconductor layers of the switching elements, where the blocking layer suppresses penetration of hydrogen separated from the hydrogenated amorphous silicon layers.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. patent application Ser. No.14/529,340 filed Oct. 31, 2014, which claims priority to Japanese PatentApplication No. 2013-231151, filed Nov. 7, 2013, the contents of all ofwhich are incorporated herein by reference in their entirety.

TECHNICAL FIELD

The present invention relates to a structure of an image sensor and amanufacturing method thereof, in particular, to a structure of an imagesensor for a radiographic imaging apparatus and a manufacturing methodthereof.

BACKGROUND

Techniques for inspecting inside an inspection target in anon-destructive manner using X-ray transmission images have becomeessential techniques in various fields such as a field of medicalservices and a field of industrial-use nondestructive testing.Especially, X-ray image sensors which can directly capture X-raytransmission images as electronic data have become widely used becauseof their properties such as fast imaging, capability to assist in X-rayinterpretation by using image processing, and capability to supportmoving images. Devices called an FPD (flat panel detector) are mainlyused as such an X-ray image sensor.

Japanese Unexamined Patent Application Publication (JP-A) No. H04-206573discloses a structure often used as the FPD (see FIG. 5 of the document)in these days. FIG. 13 depicts the structure, in which switchingelements 700, photoelectric transducers 300 are arranged on substrate200 in layers and a phosphor layer 600 for converting X-rays into lightis further arranged on the layered structure with a passivation film 750and a flattening film 760 inserted between the phosphor layer 600 andthe layered structure. Each switching element 700 includes a gateelectrode 710, a gate insulating film 720, an a-Si:H (hydrogenatedamorphous silicon) film 730, and source and drain metals 740. Eachphotoelectric transducer 300 includes a lower electrode 310, an a-Si:Hfilm 330 and an upper electrode 350. In the disclosed structure,electric signals according to the exposure intensities of X-rays areobtained by converting X rays which have passed through a specimen intolight with the phosphor layer 600, converting the light into electriccharges with the photoelectric transducers 300, and then outputting theelectric charges from the structure by opening or closing the switchingelements 700.

In FPDs widely used nowadays, a-Si:H TFTs are used as TFTs (thin-filmtransistors), which are switching elements, and a-Si:H photodiodes areused as photoelectric transducers. It should be noted that, althoughthis example provides a structure that the switching elements, thephotoelectric transducers and the phosphor layer are layered on thesubstrate in this order, FPDs can have another layered structure that asubstrate, a phosphor layer, photoelectric transducers and switchingelements are layered in this order as disclosed in FIG. 1 of JP-A No.H06-342078. In addition, there are FPDs employing a different techniquefor converting X-rays into electric signals, which do not use a phosphorlayer. For example, JP-A No. S62-86855 (see FIG. 2 of the document)discloses a structure that uses a photoconductor layer which convertsX-rays into the electric charges directly, and discloses a method thatuses a layer of Bi₁₂Ge₂₀ as an example of the photoconductor layer.However, the direct type FPDs which convert X-rays into electric chargesdirectly have a disadvantage of quantum efficiency being lower than theindirect type FPDs which use a phosphor layer. There are several typesof FPD structure as described above. However, all of them have astructure in which at least switching elements and photoelectrictransducers are formed in layers on a substrate.

During recent years, in the field of medical services, there areincreasing demands on X-ray diagnosis devices to realize higherresolution and support fluoroscopy (taking moving or real-time images)on radiographic imaging. This is because higher resolution is essentialfor observing an affected part in more detail, and fluoroscopy isrequired for checking an optimal condition for radiographic imaging andfinding out a proper timing for radiographic imaging. In order toincrease the resolution of FPDs, there is a need to read signals at highspeed from an increased number of photodetectors which have beenprepared for realizing the high resolution. In order to supportfluoroscopy, it is necessary to read the signals from all thephotodetectors during a predetermined frame period. That is, it isnecessity to read the signals at far more higher speed in order to allowan FPD having higher resolution to support fluoroscopy.

The main cause of the limitation of the signal read-out speed of FPDs ison-state resistance of the switching elements. In conventional FPDs,a-Si:H TFTs are used for the switching elements. The field-effectmobility of a-Si:H is as low as 1 cm²/Vs or less. This causes highon-state resistance of the a-Si:H TFTs. Alternatively, there are poly-Si(polycrystalline silicon) TFTs, which are switching elements that can beformed on a large-sized substrate. The field-effect mobility of poly-Siis reported to have as high as more than 100 cm²/Vs. Thus, the on-stateresistance of the poly-Si TFTs is very small.

However, poly-Si TFTs have another problem that their threshold voltagesvary largely. Such variations in threshold voltages cause variations inthe signal electric charges in FPDs, causing FPN (fixed pattern noise).The FPN can be corrected by modifying a signal readout circuit, but itcauses other problems about narrow dynamic range and/or high cost of thesignal readout circuit. Variations in the threshold voltages of poly-SiTFTs that lead to the FPN are an essential problem resulting from thecrystal structure of poly-Si TFTs being a polycrystal, and thus thepoly-Si TFTs are hardly used for FPDs.

In recent years, amorphous oxide semiconductor has been developedrapidly. In—Ga—Zn—O is the representative case. The field-effectmobility of amorphous oxide semiconductor is about 10 cm²/Vs to 20cm²/Vs and is an order-of-magnitude larger than that of a-Si:H or more.Therefore, the on-state resistance of a TFT formed by the amorphousoxide semiconductor is an order of magnitude smaller than that of ana-Si:H TFT or less. Further, since its structure is amorphous, theproblem that threshold voltages vary largely does not arise like poly-SiTFTs do.

JP-A No. 2009-71057 discloses an example of applying amorphous oxidesemiconductor to an image sensor (see FIG. 3 of the document). The imagesensor described therein has a structure in which a plurality ofphotodetectors are arranged on a substrate in layers, where eachphotodetector includes a switching element and a photoelectricconversion section having sensitivity to a specific wavelength. A unitstructure of the photodetector is illustrated in FIG. 14. This structureis formed by arranging a TFT as a switching element 100 and aphotoelectric transducer 800 on the substrate 200 in layers, withpassivation film 150 inserted between them. The TFT is composed of agate electrode 110, a gate insulating film 120, an amorphous oxidesemiconductor film 130 and source and drain electrodes 140. Thephotoelectric transducer 800 is composed of a lower electrode 810, aphotoelectric conversion film 820 and an upper electrode 830. Ifamorphous oxide semiconductor is applied to an image sensor as in thiscase, it may be possible to achieve high speed signal read-out.

Although amorphous oxide semiconductor has excellent characteristics, ithas problems of being unable to control off-state current depending onthe manufacture method. The cause of this problem is that control ofoxygen deficiency (oxygen holes) of the amorphous oxide semiconductor isdifficult as described in JP-A No. 2008-42088 (see paragraph 0006) andJP-A No. 2008-60419 (see paragraph 0005 of the document). As acountermeasure, JP-A No. 2008-42088 discloses a structure that twoinsulating layers that are laminated so as to sandwich an amorphousoxide semiconductor layer, and a technique of making oxygen holeconcentration of either one of two interfaces of the insulating layersin contact with the amorphous oxide semiconductor layer smaller thanoxygen hole concentration in an amorphous oxide semiconductor film (seeclaim 10 of the document). In addition, JP-A No. 2008-60419 discloses astructure that a first insulating layer and a second insulating layerare laminated on an amorphous oxide semiconductor film, and a method ofoxidizing the first insulating layer before laminating the secondinsulating layer thereon (see claim 1 of the document).

However, in cases where amorphous oxide semiconductor is applied to TFTsin an FPD having a structure where TFTs, which are switching elements,are formed on a substrate, and then photoelectric transducers made ofa-Si:H are formed as illustrated in FIG. 13, the inventors of thepresent application found that characteristics of the TFTs vary largelyand thus the image sensor cannot be operated stably even ifmanufacturing methods described in, for example, JP-A Nos. 2008-42088and 2008-60419 are applied to the FPD. The result was the same in caseswhere photoelectric transducers made of a-Si:H are formed on thesubstrate, and then TFTs made of amorphous oxide semiconductor areformed thereon.

As a result of a further analysis of the inventors, the cause of theabove matter has been found as follows. That is, in a case where a filmof amorphous oxide semiconductor is formed on a substrate, and then ana-Si:H film is formed thereon, hydrogen contained in raw material gas ofthe a-Si:H film permeates the film of amorphous oxide semiconductor,which causes the characteristics deterioration of the TFTs. In anothercase where an a-Si:H film is formed and then a film of amorphous oxidesemiconductor is formed thereon, hydrogen is separated from the a-Si:Hfilm, which forms photoelectric transducers, as a result of thetemperature rise caused upon a situation, such as a situation that thefilm of amorphous oxide semiconductor is formed and a situation that aninsulating film to be laminated on the TFTs is formed, and the hydrogenpermeates up to the film of the amorphous oxide semiconductor, whichalso causes the characteristics deterioration of the TFTs.

The present invention seeks to solve the problems.

SUMMARY

In view of the above-described issues, there are provided illustrativeimage sensors and illustrative manufacturing methods of such an imagesensor, where the image sensors have a structure that each photoelectrictransducer includes a hydrogenated amorphous silicon layer and eachswitching element includes an amorphous oxide semiconductor layer, andcan suppress characteristic deterioration of the switching element.

An image sensor according to one aspect of the present invention is animage sensor comprising: a substrate; and photoelectric transducers andswitching elements formed in layers on the substrate in this order. Eachof the photoelectric transducers includes a hydrogenated amorphoussilicon layer. Each of the switching elements includes an amorphousoxide semiconductor layer. The image sensor further comprises a blockinglayer arranged between the hydrogenated amorphous silicon layers of thephotoelectric transducers and the amorphous oxide semiconductor layersof the switching elements, where the blocking layer suppressespenetration of hydrogen separated from the hydrogenated amorphoussilicon layers.

In the image sensor, the blocking layer may be arranged between thephotoelectric transducers and the switching elements. Further, theblocking layer may include a film made of at least one material selectedfrom a group consisting of SiC, Al₂O₃, Y₂O₃ and AlN. In addition, theimage sensor may have a structure that the photoelectric transducersreceive light traveling toward a top of the substrate, where the top ofthe substrate is a side where the photoelectric transducers are formed;and the blocking layer may have a laminated structure in whichinsulating films are formed on the top surface and the bottom surface ofthe film made of the at least one material, for example, a laminatedstructure in which the film made of the at least one material issandwiched by SiN films.

In the image sensor, each of the photoelectric transducers may include ahydrogenated amorphous silicon carbide layer laminated on a top or onthe top and bottom of the hydrogenated amorphous silicon layer, wherethe hydrogenated amorphous silicon carbide layer functions as theblocking layer.

The image sensor may further comprise a phosphor layer on a bottomsurface of the substrate or over the switching elements so as to be usedfor a radiographic imaging apparatus, where the bottom surface is anopposite surface of the substrate to a surface at a side where thephotoelectric transducers are formed. Further, the image sensor mayfurther comprise a plurality of pixels arranged in matrix, wherein thehydrogenated amorphous silicon layers of the photoelectric transducersmay form a layer being continuous over the plurality of pixels, and ineach of the plurality of pixels, the hydrogenated amorphous siliconcarbide layer on the top of the hydrogenated amorphous silicon layer andan upper electrode of the photoelectric transducer may be isolated fromthose in the other pixels.

A method of manufacturing an image sensor according to another aspect ofthe present invention is a method of manufacturing an image sensorincluding a substrate, and photoelectric transducers and switchingelements arranged in layers on the substrate. The method comprises:forming the photoelectric transducers each including a hydrogenatedamorphous silicon layer, on the substrate; forming the switchingelements each including an amorphous oxide semiconductor layer, inlayers over the photoelectric transducers, after the forming thephotoelectric transducers; and forming a blocking layer between theforming the photoelectric transducers and the forming the switchingelements, where the blocking layer suppresses penetration of hydrogenseparated from the hydrogenated amorphous silicon layers.

A method of manufacturing an image sensor according to another aspect ofthe present invention is a method of manufacturing an image sensorincluding a substrate, and photoelectric transducers and switchingelements arranged in layers on the substrate. The method comprises:forming the photoelectric transducers each including a hydrogenatedamorphous silicon layer, on the substrate; and forming the switchingelements each including an amorphous oxide semiconductor layer, inlayers over the photoelectric transducers, after the forming thephotoelectric transducers. The forming the photoelectric transducersincludes forming a hydrogenated amorphous silicon carbide layerlaminated on a top of the hydrogenated amorphous silicon layer of eachof the photoelectric transducers, where the hydrogenated amorphoussilicon carbide layer functions as a blocking layer suppressingpenetration of hydrogen separated from the hydrogenated amorphoussilicon layers.

Other features of illustrative embodiments will be described below.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described, by way of example only, withreference to the accompanying drawings which are meant to be exemplary,not limiting, and wherein like elements numbered alike in severalfigures, in which:

FIG. 1 is a cross-sectional view illustrating a structure of an imagesensor according to EMBODIMENT 1;

FIG. 2 is a cross-sectional view illustrating a structure of an imagesensor according to EMBODIMENT 2;

FIG. 3 is a cross-sectional view illustrating a structure of an imagesensor according to EXAMPLE 1;

FIG. 4 is a cross-sectional view illustrating a structure of an imagesensor according to EXAMPLE 2;

FIG. 5 is a cross-sectional view illustrating a structure of an imagesensor according to EXAMPLE 3;

FIG. 6 is a cross-sectional view illustrating a structure of an imagesensor according to EXAMPLE 4;

FIG. 7 is a cross-sectional view illustrating a structure of an imagesensor according to EXAMPLE 5;

FIG. 8 is a top view illustrating the structure of the image sensoraccording to EXAMPLE 5;

FIG. 9 is a block diagram illustrating a circuit arrangement of theimage sensor of the present invention;

FIG. 10 is a circuit diagram of a signal readout circuit applicable tothe image sensor according to the present invention;

FIG. 11 is a timing chart illustrating operations of the image sensoraccording to the present invention;

FIG. 12 is a cross-sectional view illustrating a structure of an imagesensor according to EXAMPLE 7;

FIG. 13 is a cross-sectional view illustrating a structure of aconventional image sensor; and

FIG. 14 is a cross-sectional view illustrating a structure of aconventional image sensor.

DETAILED DESCRIPTION

Illustrative embodiments of image sensors and manufacturing methods ofan image sensor will be described below with reference to the drawings.It will be appreciated by those of ordinary skill in the art that thedescription given herein with respect to those figures is for exemplarypurposes only and is not intended in any way to limit the scope ofpotential embodiments may be resolved by referring to the appendedclaims.

According to the illustrative image sensors and the illustrative methodsof manufacturing an image sensor as embodiments of the presentinvention, it is possible to read signals of a high resolution imagesensor at high speed. Accordingly, it is possible to provide an FPD usedfor X-ray detection, which has higher resolution and supportsfluoroscopy (taking moving or real-time images).

With respect to the reason, an illustrative image sensor uses amorphousoxide semiconductor for switching elements. The field-effect mobility ofthe amorphous oxide semiconductor is about 10 cm²/Vs to 20 cm²/Vs, whichis an order-of-magnitude larger than that of a-Si:H or more.Accordingly, it is possible to read signals from a high resolution imagesensor at high speed.

According to the illustrative methods of manufacturing an image sensoras embodiments of the present invention, it is possible to suppressmanufacturing variations of image sensors that use amorphous oxidesemiconductor for switching elements, and thus improve the yield.

This is because a a-Si:H layer to be photoelectric transducers, isformed before forming switching elements in the illustrative imagesensor. Accordingly, it is possible to prevent hydrogen contained in rawmaterial gas of the a-Si:H layer from permeating a layer the amorphousoxide semiconductor. Further, in the illustrative image sensor, ablocking layer that suppresses penetration of hydrogen is arrangedbetween the hydrogenated amorphous silicon layers of the photoelectrictransducers and the amorphous oxide semiconductor layers of theswitching elements, for example, between the photoelectric transducersand the switching elements. Accordingly, it is possible to preventhydrogen separating from the a-Si:H layer due to, for example, heat atthe time of forming the switching elements, and from permeating theamorphous oxide semiconductor. Furthermore, the blocking layer can beconstituted as a part of each photoelectric transducer as a layer ofSiC, and thus it is possible to reduce the manufacturing cost.

Hereafter, embodiments of the present invention will be described indetail with reference to the drawings. It should be noted that, in orderto have visibility of the drawings, the size and the scale of eachcomponent in each drawing are changed as appropriate. In each of thecross-sectional views, components are distinguished by their hatching.

Embodiment 1

FIG. 1 is a cross-sectional view of an image sensor according toEMBODIMENT 1. The image sensor of the present embodiment has a structurethat a photoelectric transducers 300 made of a-Si:H, and switchingelements 100 as amorphous oxide semiconductor TFTs are arranged inlayers on a substrate 200. A blocking layer 500 that suppressespenetration of hydrogen is arranged between the photoelectrictransducers 300 and the switching elements 100.

Each photoelectric transducer 300 is constituted by: a lower electrode310; a p-a-Si:H layer 320, which is a layer of p type hydrogenatedamorphous silicon; an i-a-Si:H layer 330, which is a layer of intrinsichydrogenated amorphous silicon; an n-a-Si:H layer 340, which a layer ofis n type hydrogenated amorphous silicon; and an upper electrode 350.This structure is provided under the assumption that light enters thephotoelectric transducers 300 from the side of the lower electrode 310,that is, the photoelectric transducers 300 receives light coming fromthe bottom side thereof. Each switching element 100 is constituted by agate electrode 110, a gate insulating film 120, an amorphous oxidesemiconductor film 130, a channel protection film 135, a drain electrode140, and a source electrode 145. It is desirable if the lower electrode310 of each photoelectric transducer 300 is electrically connected to acommon electrode 410, and if a protective film 420 and a flattening film430 are formed after forming the photoelectric transducers 300. Inaddition, when using the image sensor as an FPD for detecting X-rays, aphosphor layer 600 is arranged on the bottom surface of the substrate200 being a glass plate, where the bottom surface is opposite to thesurface where the photoelectric transducers are formed.

Next, a manufacturing process of the image sensor having theabove-described structure will be described. A photoelectric transducers300 are formed on the substrate 200. Specifically, a common electrode410 is formed on the substrate 200. For example, the substrate 200 canbe made of glass, and the common electrode 410 can be made of amaterial, such as Al and Cr, which has relatively small resistivity. Thelower electrode 310 of each photoelectric transducer is formed thereon.The lower electrode 310 can be made of a material for transparentelectrodes, such as ITO (Indium Tin Oxide). Thereafter, the p-a-Si:Hlayer 320, the i-a-Si:H layer 330 and the n-a-Si:H layer 340 arelaminated and patterned. At this time, it is desirable to form the threelayers continuously in the same vacuum chamber. The upper electrode 350of each photoelectric transducer is formed thereon. For example, theupper electrode 350 can be made of Cr. Next, the protective film 420 andthe flattening film 430 are formed thereon. For example, the protectivefilm 420 can be a single-layer film of SiO₂ or SiN, or a multilayer filmconstituted by these materials. For example, the flattering film 430 canbe made of acrylate resin. Here, there are cases where the flatteringfilm 430 need not be provided depending on flatness of the arrangementof the photoelectric transducers and the switching elements.

Next, in the present embodiment, a blocking layer 500 is formed thereon.The blocking layer 500 can be made of a material that can suppresspenetration of hydrogen, such as SiC, Al₂O₃, Y₂O₃ and AlN.

The switching elements 100 are formed thereon. Specifically, the gateelectrode 110 and the gate insulating film 120 of each switching elementare formed in order. For example, the gate electrode 110 can be made ofAl or Cr, or alloy of these metals, and the gate insulating film 120 canbe made of SiO₂. Here, there are cases where insulation of the gateelectrodes 110 deteriorates depending on the kind of the blocking layer500. In that case, an insulating layer, such as a layer of SiO₂, may bearranged between the blocking layer 500 and the gate electrodes 110.Next, an amorphous oxide semiconductor film 130 of each switchingelement is formed. The amorphous oxide semiconductor film 130 can be afilm of InGaZnO or an oxide film including at least one of In, Ga andZn. Annealing treatment may be applied after forming the amorphous oxidesemiconductor film 130. Thereafter, the channel protection film 135 ofeach switching element may be formed. For example, the channelprotection film 135 can be a film of SiO₂, if the channel protectionfilm 135 is formed. After forming the channel protection film 135 andthe amorphous oxide semiconductor film 130, a metallic film that is tobe formed into a drain electrode 140 and a source electrode 145 of eachswitching element is layered and patterned into the electrodes. It ispreferable that the metallic film that is to be formed into the drainelectrode 140 and the source electrode 145 is made of a metal with lowresistivity, for example, alloy of Al, and Mo and/or Ti. A passivationfilm 150 is formed thereon. For example, the passivation film 150 can bea single-layer film of SiO₂ or a multilayer film constituted by SiO₂ andSiN. After forming the passivation film 150, annealing treatment may beapplied.

When the image sensor is used as an FPD for X-ray detection, a phosphorlayer 600 is provided on the opposite surface of the substrate 200 tothe surface where the photoelectric transducers 300 of the substrate 200are arranged. For example, the phosphor layer 600 can be made of cesiumiodide.

According to the present embodiment, it is possible to read signals of ahigh resolution image sensor at high speed, which allows FPDs used forX-ray detection to have higher resolution and to support fluoroscopy(taking moving or real-time images). Further, it is possible to suppressmanufacturing variations of the image sensors and thus improve theyield. The reason for this will be described below.

In a large-sized image sensor (of 20 cm×20 cm or more), such as an FPDused for X-ray detection, the switching elements are made of a-Si:H. Asthe field-effect mobility of the a-Si:H is small such that it is 1cm²/Vs or less, the signal read-out speed of the image sensor has beenlimited. The switching elements in the image sensor according to thepresent embodiment are made of amorphous oxide semiconductor. Thefield-effect mobility of amorphous oxide semiconductor is about 10cm²/Vs to 20 cm²/Vs, which is an order-of-magnitude larger than that ofa-Si:H or more. Accordingly, it is possible to read signals of a highresolution image sensor at high speed.

Even if amorphous oxide semiconductor is used for the switching elementsin the image sensor of the present embodiment, variations incharacteristics of the switching devices can be suppressed. In an imagesensor having a conventional structure, when TFTs of amorphous oxidesemiconductor are used as the switching elements, it causes a problemthat the characteristics of the TFTs become unstable. This is becausewhen photoelectric transducers of a-Si:H are formed, hydrogen containedin raw material gas of the photoelectric transducers permeates a layerof the amorphous oxide semiconductors and causes oxygen deficiency. Onthe other hand, if the photoelectric transducers are formed first andthe layer of amorphous oxide semiconductor is formed thereafter in animage sensor having a conventional structure, hydrogen also separatesfrom a-Si:H and permeates in the layer of the amorphous oxidesemiconductor because of heat conducted to the substrate at the timewhen the layer of amorphous oxide semiconductor is formed or upon othertreatment of, for example, annealing. In the image sensor of the presentembodiment, photoelectric transducers are formed on the substrateearlier, and then a blocking layer for suppressing penetration ofhydrogen is formed thereon, and then a layer of amorphous oxidesemiconductor is formed. In particular, when the blocking layer includesa film made of at least one material of SiC, Al₂O₃, Y₂O₃, and AlN, thehydrogen permeation coefficient of the film is substantially smallcompared with a film of SiO₂ or SiN having the same film thickness.Accordingly, it is possible to suppress the penetration of hydrogencoming from the photoelectric transducers and suppress variations incharacteristics among the switching elements. For this reason, it ispossible to manufacture an image sensor that uses amorphous oxidesemiconductor with high yield.

Embodiment 2

FIG. 2 depicts a cross-sectional view of an image sensor according toEMBODIMENT 2. The image sensor of the present embodiment has a structurethat photoelectric transducers 300 made of a-Si:H, and switchingelements 100 as amorphous oxide semiconductor TFTs are arranged on asubstrate 200 in layers.

The structure of the switching element is the same as the structureshown in EMBODIMENT 1. Each photoelectric transducer 300 is constitutedby: a lower electrode 310; a p-a-SiC:H layer 325, which is a layer of ptype hydrogenated amorphous silicon carbide; an i-a-Si:H layer 330,which is a layer of intrinsic hydrogenated amorphous silicon; ann-a-SiC:H layer 345, which is a layer of n type hydrogenated amorphoussilicon carbide; and an upper electrode 350. That is, each photoelectrictransducer 300 has a structure that includes, as an upper layer of thei-a-Si:H layer 330 being a layer of hydrogenated amorphous silicon (onthe top of the layer of hydrogenated amorphous silicon), an n-a-SiC:Hlayer 345 which functions as a blocking layer. This structure isprovided under the assumption that light enters the photoelectrictransducers 300 from the side of the lower electrode 310, that is, thephotoelectric transducers 300 receives light coming from the bottom sidethereof. In addition, a layer of p-a-Si:H may be used instead of thep-a-SiC:H layer 325. It is desirable if the lower electrode 310 of eachphotoelectric transducer 300 is electrically connected to a commonelectrode 410, and a protective film 420 and a flattening film 430 areformed on the upper electrode 350 of each photoelectric transducer 300.In addition, when using the image sensor as an FPD for detecting X-rays,a phosphor layer 600 is arranged on the bottom surface of the substrate200 being a glass plate, where the bottom surface is opposite to thesurface where the above structures are formed.

It should be noted that the image sensor having the above-describedstructure can be manufactured by: forming the photoelectric transducers300 on the substrate 200; forming switching elements 100 in layers overthe photoelectric transducers 300; and if necessary, providing aphosphor layer 600 on the opposite surface of the substrate 200 to thesurface where the photoelectric transducers 300 is arranged. In themanufacturing processes, each photoelectric transducer 300 includes then-a-SiC:H layer 345 working as the blocking layer and laminated on thetop of the i-a-Si:H layer 330 being a layer of hydrogenated amorphoussilicon.

According to the present embodiment, as in EMBODIMENT 1, it is possibleto read signals of a high resolution image sensor at high speed, whichallows FPDs used for X-ray detection to have higher resolution and tosupport fluoroscopy (taking moving or real-time images). In addition, itis possible to suppress manufacturing variations of the image sensorsand thus improve the yield. Further, it is possible to reduce themanufacturing cost of the image sensor. The reason will be describedbelow.

The reason why the signal read-out speed of the image sensor can beincreased is the same as the reason described in EMBODIMENT 1. Inaddition, the reason why manufacturing variations can be suppressed andthe yield can be improved is the same as the reason described inEMBODIMENT 1.

The reason why the manufacturing cost can be reduced is that theblocking layer that suppresses penetration of hydrogen is substituted bya part of each photoelectric transducer in the present embodiment.Although a layer of silicon carbide SiC of each photoelectric has afunction of suppressing the penetration of hydrogen, this is also usedas an n type semiconductor layer (the top semiconductor layer) of eachphotoelectric transducer in the present embodiment. Accordingly, thereis no need to newly provide a blocking layer as in EMBODIMENT 1.Accordingly, it is possible to reduce the manufacturing cost. The layerof SiC can also be used as a p type semiconductor layer in eachphotoelectric transducer by changing the impurity. Many P-I-N typephotoelectric transducers have a structure to receive incident light ona p type semiconductor layer, considering the mobility of the carrier.However, when the layer of SiC is used as the p type semiconductorlayer, the optical band gap spreads more than that of an a-Si layer, andthus it is possible to increase quantum efficiency. In order tomanufacture the structure of the present embodiment, there is prepared araw material gas system for forming the n-a-SiC:H layer 345 whichfunctions as a blocking layer. Thus, it is possible to change the p typesemiconductor layer into SiC easily without additionally preparing a rawmaterial gas system. Accordingly, it is possible to create an imagesensor having high quantum efficiency at low cost.

EXAMPLES Example 1

FIG. 3 depicts a structure of another example of the image sensoraccording to EMBODIMENT 1. The structure is the same as that of theformer example in the respect that the photoelectric transducers 300,the blocking layer 500 and the switching elements 100 are formed on thesubstrate 200 in layers, but is different in that the phosphor layer 600which converts X-rays into light is formed over the switching elements100. With respect to this structure, the image sensor is irradiated withX-rays from its surface where the phosphor layer 600 is arranged. Sincelight coming from the phosphor layer 600 (and traveling toward the topof the substrate) enters the photoelectric transducers 300 from theupper side, it is desirable to make the structure of each photoelectrictransducer 300 as in the following. The lower electrode 310 of eachphotoelectric transducer 300 can be made of a material having smallresistivity, such as Al and Cr, since it does not need to transmitlight. In this case, the common electrode 410 and the lower electrode310 of each photoelectric transducer 300 can be formed in the same metallayer. The n-a-Si:H layer 321, the i-a-Si:H layer 330, and the p-a-Si:Hlayer 341 are laminated on the lower electrode 310 of each photoelectrictransducer 300. In so doing, a structure in which holes move to thelight-entering side of the photoelectric transducers 300 can beobtained. Thus, hole-electron pairs generated in the i-a-Si:H layer 330can be efficiently collected, and thus afterimage characteristicsimprove also. In addition, a flattening film 160 may be arranged betweenthe switching elements 100 and the phosphor layer 600.

In addition, the blocking layer 500 can be made of at least one of SiC,Al₂O₃, Y₂O₃ and AlN, which are the same materials as the materials shownin EMBODIMENT 1. However, since light irradiated onto the photoelectrictransducer 300 passes through the blocking layer 500 in the structure ofthe present example, it is desirable to use a structure which canprevent light from being absorbed in the blocking layer 500 or beingreflected on the blocking layer 500. All of the above-describedmaterials applicable to the blocking layer 500 has almost no absorptiveproperty for visible light but have the refractive index larger thanthat of, for example, SiO₂ or acrylate resin. In particular, therefractive index of SiC is about 2.6, which is way larger than 1.45 ofSiO₂ and about 1.5 of acrylate resin. Accordingly, by forming theblocking layer 500 so as to have a multilayer structure of SiN, SiC andSiN films (that is, a laminated structure that a SiC film is sandwichedby SiN films), reflection of light thereon can be reduced substantially.This is because the refractive index of SiN is about 2, which is aninterim value between the refractive index of SiO₂ or acrylate resin andthe refractive index of SiC, and a layer of SiN serves asanti-reflection coating. It should be noted that the refractive indicesof other materials are: Al₂O₃: about 1.7; Y₂O₃: about 1.8; and AlN:about 2.1, and thus needless to say, it is possible to obtain ananti-reflection effect by combining any one of those materials with thinfilms having appropriate refractive indices to prepare a multilayerstructure as in the case of SiC described above.

According to the present example, as in EMBODIMENT 1, it is possible toread signals of a high resolution image sensor at high speed, whichallows FPDs used for X-ray detection to have higher resolution and tosupport fluoroscopy (taking moving or real-time images). In addition, itis possible to suppress manufacturing variations of image sensors andthus improve the yield. Further, it is possible to improve spatialresolution of the image sensor. The reason will be described below.

The reason why the signal read-out speed of the image sensor can beincreased is the same as the reason described in EMBODIMENT 1. Inaddition, the reason why manufacturing variations can be suppressed andthe yield can be improved is the same as the reason described inEMBODIMENT 1.

Next, the reason why the spatial resolution can be improved will bedescribed. If the phosphor layer 600 is arranged on the surface thesubstrate 200 as in EMBODIMENT 1, where the surface is opposite to thesurface at the side of the photoelectric transducers 300 and theswitching elements 100, light emitted from the phosphor layer 600 ispropagated in the substrate 200 in its thickness direction and entersthe photoelectric transducer 300. Here, the phosphor layer 600 emitslight diffused regardless of the propagating direction of X-rays.Accordingly, if the substrate 200 is thick, the probability that lightdoes not reach to a concerned photoelectric transducer located on astraight line in the propagating direction of the X-rays increases butreaches to neighboring photoelectric transducers. As a result, thespatial resolution decreases. However, in this example, the phosphorlayer 600 is arranged above the switching element 100. Between thephotoelectric transducers 300 and the phosphor layer 600, there arearranged the protective film 420, the flattening film 430, the blockinglayer 500, and the gate insulating film 120, the passivation film 150,and the flattening film 160 of each switching element. It is possible toform all those film thicknesses in a total of 10 micrometers or less.This is overwhelmingly thinner than the thickness of the substrate 200.In addition, SiC, Al₂O₃, Y₂O₃ and AlN, which can be used for theblocking layer 500, have large transmittance over a range from infraredregion to ultraviolet region. Therefore, the quantum efficiency israrely reduced. Accordingly, the probability of light spreading in thecircumferential of the photoelectric transducer on which the lightshould be irradiated primarily can be reduced, and thus the spatialresolution increases.

Example 2

FIG. 4 depicts a structure of another example of the image sensoraccording to EMBODIMENT 1. The structure is the same as that of EXAMPLE1 in the respect that the photoelectric transducers 300, the blockinglayer 500 and the switching elements 100 are formed on the substrate 200in layers and then the phosphor layer 600 is further arranged on thelayered structure, but is different in the structure of eachphotoelectric transducers 300. In this example, each photoelectrictransducer 300 serves as a Schottky diode. On a lower electrode 310 ofeach photoelectric transducer 300, an i-a-Si:H layer 330, a p-a-Si:Hlayer 341 and an upper electrode 350 are laminated in the order. Lightcoming from the phosphor layer 600 enters the photoelectric transducers300 from the side of the upper electrode. In order to make the barrierheight of the Schottky diode suitable, it is important to select metalto be formed into the lower electrode 310 so as to be suitable for thesemiconductor layers. Specifically, a combination is selected such thatthe work function of metal is higher than the electron affinity of thesemiconductor layers. When the semiconductor layers are made of a-Si:H,it is possible to prepare an excellent Schottky diode by using, forexample, Cr for the lower electrode 310. The upper electrode can be madeby using a transparent electrode, such as an ITO electrode.

According to this example, as in EXAMPLE 1, it is possible to make FPDsused for X-ray detection to have higher resolution and to supportfluoroscopy (taking moving or real-time images), and improve the yield.In addition, it is possible to improve spatial resolution of the imagesensor. Further, it is possible to reduce the manufacturing cost. Thereason will be described below.

The reason why the signal read-out speed of the image sensor can beincreased is the same as the reason described in EMBODIMENT 1. Inaddition, the reason why manufacturing variations can be suppressed andthe yield can be improved is the same as the reason described inEMBODIMENT 1. The reason why the spatial resolution can be improved isthe same as the reason described in EXAMPLE 1.

In this example, a Schottky diode is used as each photoelectrictransducer 300. As described above, this structure has no n-a-Si:Hlayer. Accordingly, the manufacturing cost can be reduced for an amountcorresponding to the semiconductor layer of n-a-Si:H being notlaminated.

Example 3

FIG. 5 depicts a structure of another example of the image sensoraccording to EMBODIMENT 2. The structure is the same as that of theformer example in the respect that the photoelectric transducers 300 andthe switching elements 100 are formed on the substrate 200 in layers,but is different in that the phosphor layer 600 is arranged over theswitching elements 100 with the flattening film 160 inserted betweenthem. Further, it is desirable if each photoelectric transducers 300 hasa structure including the lower electrode 310, the n-a-Si:H layer 321,the i-a-Si:H layer 330, the p-a-SiC:H layer 346 and the upper electrode350. In the structure, a n-a-SiC:H layer may be used instead of then-a-Si:H layer 321.

According to the present example, as in EMBODIMENT 2, it is possible tomake FPDs used for X-ray detection to have higher resolution and tosupport fluoroscopy (taking moving or real-time images), improve theyield, and reduce the manufacturing cost. Further, it is possible toimprove spatial resolution of the image sensor as in EXAMPLE 2.

The reason why the image sensor of this example can increase theresolution, support fluoroscopy (motion picture imaging), improve theyield, and reduce the manufacturing cost is the same as the reasondescribed in EMBODIMENT 2. The reason why the spatial resolution can beimproved is the same as the reason described in EXAMPLE 1.

Example 4

FIG. 6 depicts a structure of another example of the image sensoraccording to EMBODIMENT 2. The structure is the same as that of EXAMPLE3 in the respect that the photoelectric transducers 300, the switchingelements 100 and the phosphor layer 600 are formed on the substrate 200in layers, but is different in the structure of each photoelectrictransducers 300. Each photoelectric transducer 300 used herein isconstituted by the lower electrode 310, the i-a-Si:H layer 330, thep-a-SiC:H layer 347, and the upper electrode 350. That is, it has astructure of a Schottky barrier diode. Metal used for the lowerelectrodes 310 is selected such that its work function is larger thanthe electron affinity of the semiconductor layers. In this example, thelower electrodes 310 are made of Cr, and in this case, the commonelectrode 410 may be formed with the same metal as the lower electrode310. The upper electrodes 350 can be made of ITO that penetrates light.

According to this example, as in EXAMPLE 3, it is possible to make theimage sensor achieve an increased resolution and support fluoroscopy(taking moving or real-time images), to improve the yield, and toimprove the spatial resolution of the image sensor. Further, it ispossible to lower the manufacturing cost more than the image sensorshown in EXAMPLE 3.

The reason why the image sensor of this example can achieve theincreased resolution, support fluoroscopy (taking moving or real-timeimages), and improve the yield is the same as the reason described inEMBODIMENT 2. The reason why the spatial resolution can be improved isthe same as the reason described in EXAMPLE 1. The reason why themanufacturing cost can be lowered more than the image sensor of EXAMPLE3 is because the number of semiconductor layers constituting eachphotoelectric transducer is two, which is less than three, which is thenumber of semiconductor layers constituting the photoelectric transducershown in EXAMPLE 3.

Example 5

FIG. 7 depicts a structure of another example of the image sensorrelated to EMBODIMENT 2. This structure includes a dummy area 301 havingthe same layer structure as the photoelectric transducers 300 andarranged between photoelectric transducers 300 in two adjoining pixels.As for at least the upper electrode and the amorphous semiconductorlayer which is in contact with the upper electrode and includesimpurities added thereto, those in the dummy area 301 are electricallyisolated from those in the photoelectric transducer 300. In the examplein FIG. 7, each photoelectric transducer 300 has a laminated structureof the lower electrode 310, the p-a-SiC:H layer 325 which is a layer ofa p type hydrogenated amorphous silicon carbide, the i-a-Si:H layer 330which is a layer of an intrinsic hydrogenated amorphous silicon, then-a-SiC:H layer 345 which is a layer of a n type hydrogenated amorphoussilicon carbide, and the upper electrode 350, in this order from thesubstrate 200 side. In this structure, the upper electrode 350 and thelayer of hydrogenated amorphous silicon carbide arranged at the upperside (the n-a-SiC:H layer 345 as a layer of n type hydrogenatedamorphous silicon carbide herein) in the photoelectric transducer 300are electrically isolated from those in the dummy area 301 in eachpixel, and at least the hydrogenated amorphous silicon layer (thei-a-Si:H layer 330, the p-a-SiC:H layer 325, and the lower electrode 310herein) is continuous over the pixels.

FIG. 8 depicts a top view of the upper electrodes 350, wherein hatchedportions indicate regions where the upper electrodes 350 are arranged.As can be seen from FIG. 7 and FIG. 8, the whole area is divided intosections of pixels 303, and each of the sections includes thephotoelectric transducer 300 and the dummy area 301 arranged with theinsulating region 302 inserted between them, where the insulating region302 is prepared by removing the upper electrode 350 and the n-a-SiC:Hlayer 345 as a layer of n type hydrogenated amorphous silicon carbidefrom the layered structure. By having such a layout, the upper electrodeof the photoelectric transducer 300 of each pixel is electricallyisolated from the upper electrode of the photoelectric transducer 300 ofthe neighboring pixel. Although not illustrated in FIG. 8, eachswitching element 100 prepared by using an amorphous oxide semiconductorTFT is arranged at a position over the corresponding dummy area 301.

Although FIG. 7 does not illustrate a phosphor layer, the image sensorof the present example includes a phosphor layer, which may be arrangedon a surface of the substrate 200 opposite to the surface where thephotoelectric transducers 300 are formed as in EMBODIMENT 1, or may bearranged over the switching elements 100 as in EXAMPLE 1. In addition,upon removing the upper electrode 350 and the n-a-SiC:H layer 345 as alayer of n type hydrogenated amorphous silicon carbide for preparingeach insulating region 302, no problem will arise even if the i-a-Si:Hlayer 330 as a layer of intrinsic hydrogenated amorphous silicon beingpartially etched in the insulating region 302.

According to the present example, as in EMBODIMENT 2, it is possible toread signals of a high resolution image sensor at high speed, and it ispossible to make FPDs used for X-ray detection to have higher resolutionand to support fluoroscopy (taking moving or real-time images). Inaddition, it is possible to suppress manufacturing variations incharacteristics of the image sensors and improve the yield. Further, itis possible to reduce the manufacturing cost of the image sensors.

The reason why it is possible to reduce the manufacturing cost of theimage sensor of this example is the same as the reason described inEMBODIMENT 2. In addition, the reason why the image sensor of thisexample can increase the resolution, support fluoroscopy (taking movingor real-time images), and improve the yield is as follows, in additionto the reason described in EMBODIMENT 2. That is, when forming theswitching elements 100 as amorphous oxide semiconductor TFTs, hydrogenseparates from the a-Si:H layer, which is a layer of hydrogenatedamorphous silicon and constitutes each of the photoelectric transducers,due to heat conducted to the substrate on forming films that constitutethe switching elements 100 and heat conducted to the substrate whencarrying out annealing treatment of the switching elements 100. Theimage sensor of the present example can further more reduce penetrationof the separated hydrogen into the amorphous oxide semiconductor layers.This is because each i-a-Si:H layer 330, which is a layer of intrinsichydrogenated amorphous silicon containing most hydrogen in the layeredstructure, has a very small cross-sectional area, and the area incontact with the protective film 420 is reduced.

Example 6

FIG. 9 depicts a circuit diagram of an example that an image sensor isformed using the structures described in EMBODIMENTS 1 and 2 andEXAMPLES 1 to 5. The image sensor 900 has a structure that pixels 910are arranged in matrix, where each of the pixels 910 contains a TFT 911which is a switching element, and a photoelectric transducer 912.Although FIG. 9 illustrates an example where 4×4 pixels are arranged ina matrix form, needless to say, the number of pixels can be changedaccording to the objective. Drain terminals of TFTs 911 lined up in apixel column in a longitudinal direction are connected to the same dataline (D1 to D4), and gate terminals of TFTs lined up in a pixel row inthe horizontal direction are connected to the same gate line (G1-G4).One end of each photoelectric transducer 912 is connected to acorresponding TFT. The other end of each photoelectric transducer 912 isconnected to a corresponding bias wire Vb. The data lines D1 to D4 areconnected to a signal readout circuit 920, and the gate lines G1 to G4are connected to a gate drive circuit 930.

The signal readout circuit 920 can be prepared by using circuitsillustrated in FIG. 10 whose number is the same as that of the datalines. FIG. 10 depicts an example that uses an integrating circuitconstituted by an operational amplifier 921, an integral capacity 922,and a reset switch 923 as the signal readout circuit. The data lines D1to D4 are connected to an input terminal In of the integrating circuitin the signal readout circuit 920. Bias voltage Vb is set to an electricpotential that makes reverse bias being applied to a p-i-n diode or aSchottky diode that constitutes the photoelectric transducer 912. Suchelectric potential is determined by an equivalent capacity of thephotoelectric transducer 912 and the maximum light exposure amountirradiated onto the image sensor. The electric potential is preferablydetermined, even when a maximum amount of light is irradiated onto theimage sensor, so as to make the electric potential to such an extentthat the electric field in a reverse bias direction remains inside thephotoelectric transducer 912.

FIG. 11 depicts a timing chart illustrating operations of the imagesensor. G1 to G4 in the figure indicate the electric potential ofrespective gate lines, and RST indicates an action of the reset switch923 of the integrating circuit. The reset switch is conductive when theRST is at its high-level. Out_1 to Out_4 indicate the outputs of thesignal readout circuit 920. Out_1 is an output of the integratingcircuit connected to the data line D1. Similarly, Out_2, Out_3, andOut_4 are outputs of the integrating circuit connected to the data lineD2, the data line D3, and the data line D4, respectively.

First, reverse bias is applied to the photoelectric transducers 912 ofall the pixels. Thereafter, the image sensor is irradiated with X-raysduring a time period Tx. Then, the phosphor layer of the image sensorconverts the X-rays into light, and electric charges stored in eachphotoelectric transducer 912 is reduced according to the amount oflight. A pulse is applied to the gate lines sequentially after a certaintime period. Time period T1 is a time period during which a pulse isapplied to the gate line G1, and thus the TFTs in a pixel row connectedto the gate line G1 become a conductive state, and electric currentflows into the data lines D1 to D4 in directions that make electriccharges that have been reduced in the corresponding photoelectrictransducers 912 be recharged. Signals corresponding to the irradiationamount of the X-rays are obtained by integrating such electric currentwith the integrating circuit. After the integration of the signals hasended, the reset switch of the integrating circuit is set to aconductive state according to the signal RST and electric charge storedin the integral capacity is reset. It is possible to obtain atwo-dimensional X-ray image by performing the above operations to allthe gate lines.

Example 7

FIG. 12 depicts a structure of another example of the image sensoraccording to EMBODIMENT 2. This structure is the same as the structureshown in EXAMPLE 3 except the structure of each photoelectrictransducers 300. In this example, each photoelectric transducer 300 isconstituted by a lower electrode 310, an insulating layer 360, ani-a-Si:H layer 330, an n-a-SiC:H layer 345, and an upper electrode 350.Here, each photoelectric transducer has a structure called an MIS (metalinsulating layer-semiconductor) diode. Here, for example, the lowerelectrode 310 can be made of Cr or Al, and the upper electrode 350 canbe a transparent electrode made of, for example, ITO.

According to this example, as in EXAMPLE 3, it is possible to make theimage sensor achieve an increased resolution and support fluoroscopy(taking moving or real-time images), improve the yield, improve thespatial resolution of the image sensor, and reduce the manufacturingcost.

The reason is the same as the reason described in EXAMPLE 3. Further, inthis structure, the semiconductor layers of each photoelectrictransducers can be prepared with only an intrinsic semiconductor layerand a p type or an n type semiconductor layer. That is, as in p-i-ndiodes, there is no need to introduce two kinds of impurity at the timeof manufacture, and thus it is possible to simplify the manufacturingfacility. However, in the MIS diode, it is necessary to apply forwardbias to the diode to perform resetting when reading signals, and thusthe signal read-out speed is somewhat slow.

It should be noted that the present invention is not limited to theabove-described embodiments and examples, and the structure and themanufacturing method of the image sensor can be modified as appropriateas long as the gist of the present invention is not deviated.

For example, although SiC, Al₂O₃, Y₂O₃ and AlN are cited as possiblematerial of the blocking layer in the above, the blocking layer needonly include material having a function of suppressing the penetrationof hydrogen.

In addition, in the above, there were shown a structure includingphotoelectric transducers of a-Si:H and a blocking layer arrangedbetween the photoelectric transducers and the switching elements, andanother type of structure that at least the top layer of thesemiconductor layers in each photoelectric transducer works as ablocking layer. Alternatively, by combining these structures, there canbe provided another structure that another blocking layer is furtherarranged between the switching elements and the photoelectrictransducers each including the semiconductor layers in which at leastthe top layer works as a blocking layer. By preparing plural blockinglayers it is possible to further improve the function of suppressing thepenetration of hydrogen in the image sensor.

In addition, in the above, the thickness of each component member of theimage sensor has not been limited in particular. However, the thicknessof each component member can be set to any value that allows theresulting sensor to work properly as an image sensor (as for theblocking layer, any value that allows the blocking layer to efficientlysuppress penetration of hydrogen). In addition, in the above, there isno description of a manufacturing apparatus to be used for forming eachcomponent member of the image sensor. However, for example, a sputteringapparatus, a vacuum evaporation apparatus, a CVD (Chemical VaporDeposition) apparatus, a PVD (Physical Vapor Deposition) apparatus, anRIE (Reactive Ion Etching) apparatus, and an ion injection apparatus,can be used as the manufacturing apparatus as appropriate.

The invention claimed is:
 1. An image sensor comprising: a substrate;photoelectric transducers on the substrate, each of the photoelectrictransducers including a hydrogenated amorphous silicon layer; andswitching elements above the photoelectric transducers, each of theswitching elements including an amorphous oxide semiconductor layer,wherein each of the photoelectric transducers is configured to convertlight entering from a side of the switching element to an electriccharge, and includes a hydrogenated amorphous silicon carbide layerlaminated on a top of the hydrogenated amorphous silicon layer of thephotoelectric transducer, the hydrogenated amorphous silicon carbidelayer having a function to suppress penetration of hydrogen separatedfrom the hydrogenated amorphous silicon layer into the switchingelement.
 2. The image sensor of claim 1, wherein each of thephotoelectric transducers further includes a hydrogenated amorphoussilicon carbide layer laminated on a bottom of the hydrogenatedamorphous silicon layer.
 3. The image sensor of claim 1, furthercomprising a plurality of pixels arranged in matrix, wherein thehydrogenated amorphous silicon layers of the photoelectric transducersform a layer being continuous over the plurality of pixels, and in eachof the plurality of pixels, the hydrogenated amorphous silicon carbidelayer on the top of the hydrogenated amorphous silicon layer and anupper electrode of the photoelectric transducer are isolated from thehydrogenated amorphous silicon carbide layers on the top of thehydrogenated amorphous silicon layers and upper electrodes of thephotoelectric transducers in the other pixels.